Sound-absorbing surface and process of producing same



Sept. 4, 1928.

L. B. RYMARCZICK SOUND ABSORBING SURFACE AND PROCESS OF PRODUCING SAMEFiled Aug. 29, 1927 INVENTOR marc'z/c/F @D ATTORNEYS Patented Sept. 4,192i.

UNITED STATES LYAL IB. BYMARCZICK, 0F LOS ANGELES, CALIFORNIA.

SOUNb-AIBSORBING SURFACE AND PROCESS OF PRODUCING SAME.

Application filed August 29, 1927. Serial No. 216,325.

This invention relates to sound absorbing surfaces, such as walls,ceilings and the like, and a new and novel process of producing same.

The invention consists in means for producing an extremely poroussurface by virtue of the inherent properties of the constituentsemployed and in afterwards subjecting the resultant product to atreatment that will greatly augment the insulating quality of theproduct.

In sound absorbing wall surfaces, it is old in the art to construct sameof plaster made up of granular particles, such as pumice, slag, coarsesand or the like, and a bonding -material such as gypsum, Keens cementsor other suitable well known materials, adapted to form a productcharacterized by many voids throughout the mass and upon the exposedsurface thereof. Plasters of this character are adapted to be applieddirectly to a wall or the like by means of hand operated tools such as atrowel} They may be made to possess, respectively, varying measures ofbonding material in proportion to respectively varying measures oramounts of granular matter. It follows, in consequence thereof, that inthe step of applying the wet plaster to a wall surface or the like bymeans of tools of the craft, there is a seepage of cementitious moistureupon the outer or eizposed face of the wall induced I by the trowelingaction when applying the plaster, and that this cementitious seepagewhen hardened forms a scale or crust which retards the intendedfunctional characteristics of a plaster of this nature. It must be bornein mind that a sound absorbing plaster to be efiicient as a deadener ofsound should be highly porous and cellular so that without a doubt avery large part of the incident sound will be absorbed. If thisincrustation, as it were, or hardened surface seepage is permitted toremain upon the exposed surface of a wall, it is reasonable to say theleast, that the functional qualities of the wall are greatly impaired,because, and as is evident, same acts to fill and hence destroy theporous or intended cellular exposed surface of the finished wall. It isaccordingly an important object of the present invention to subject thissurface incrustation or hardened aftermath following thestep of applyingthe plaster, or incident thereto, to a treatment to rupture, fracture orpenetrate same and produce therein a multiplicity of surface voids andfor effecting communication between same and the underlying voids in thebody of the material. It is reasonable. to infer that unless'thisincrustation is attacked and broken down, at least in part, after thewall is set, the fullest efiiciency of the wall as a sound deadenercannot be obtained. But, and in view of the invention now made and aboutto be fully described herein, it is possible in sound absorbing plastersto obtain the highest measure of sound absorbing efficiency.

The invention further contemplates the scheme of determining the soundabsorbing qualities of the plaster after the same has set and hardened,whereby and after the sound absorbing property of the plaster has beentested. and found lacking in its property to absorb certain sounds, saidproperty can be elevated and gauged where it will' function mostsatisfactorily to a far greater degree than would be possible withplasters heretofore known and employed where no provision was made topenetrate the aforementioned surface incrustation caused by thehardening of the cementitious seepage which is naturally caused to beexpressed from the plaster when spreading same. The advantages flowingfrom the invention are especially noticeable when the invention is usedin conjunction with plasters employing a large amount of gypsum or otherbonding material, but-the benefits to be derived are not confined tosuch plasters, as even in instances where the measure by weight ofbonding material is relatively negligible the power of the plaster toabsorb incident sound is increased when one res rts to me use of theinvention.

To the best of my knowledge, I am the first in the art to provide waysand means for treating plaster after the latter has set and hardened, orafter the plaster has been applied, for boosting, so to speak, the soundabsorbing virtues of the finished product. Here'tofore it has beensufficient that the plaster, when set and hardened, shall possiblyfunction to accomplish some part of an end in view according to someprecalcu-r lated formula pertaining to the art of acoustics,supplemented by a consideration of the physical properties of thematerial employed 1n the manufacture of the plaster, but, in noinstance, has an attempt been made to accentuate the sound deadening orabsorbing virtues of the plaster after it has been actually produced asawall surface.

Other objects and advantages will more fully appear as the descriptionproceeds.

In the drawings,

Figure 1 is a plan view of a portion of a wall surface made inaccordance with the invention;

Figure 2 is a transverse section therethrough; and

Figure 3 is a diagrammatic view similar to Figure 3, showing the mannerof breaking down the outer face of the wall surface and the innertexture of the surface.

As an example of the process and its resulting product, I will makereference to some well known ways of producing porous material having alarge number of air cells so that without resorting to the use of myinvention the material per se will function as a sound absorber. I willalso indicate some marked ways of changing the character of the materialso that an extremely high measure of efficiency will be had whenresorting to the use of the invention. The well known examples of porousmaterials capable of being treated according to the step of my inventionso that the porosity of the finished product may be increased, eitherbefore or after it has been tested, may consist of:

Example No. 1.

Example N0. 2.

A plaster formed of particles of body materlal and a binding substancebonding the particles to each other only at their points of contact. Aplaster of this character is shown and described in United StatesLetters Patent 'Reissue No. 14,992,

issued November 23, 1920, to Wallace C. Sabine and Rafael Guastavino.

Example N0. 3.

A plaster formed of pumice stone, slag Example A.

2 parts by weight pumice; 1 part by weight bonding material; or

Example B.

3 parts by weight pumice; 1 part by weight bonding material; or

Example 0.

1 part'by weight pumice;

1 part by weight bonding material.

To each of the above is added a suitable percent of soap whose functionis two-fold, namely, that it causes bubbles to be formed in the plasteras it is troweled or worked so as to increase the cellular formation ofthe product and provide readily fragile films of cement that can bequickly penetrated and torn down, and, secondly, that it furnishes whatis known in the art as slip enabling the plaster to run quickly andsmoothly at the same time lending some cohering or viscous quality tothe plaster that will cause it to take quick purchase against thesurface being coated. In either of the Examples A, B and 0 above setforth, it will be observed that, in effect, they may be called high sandplasters.

Whether a wall surface is constructed according to the aforementionedExamples 1, 2 and 3 or in accordance with the Examples A, B or C, it isimpossible to prevent the excess moisture from being expressed from theplaster during the troweling process, and, in consequence thereof, saidmoisture, which is heavily laden with cement, settles on the front orexposed face of the w ll and, when hardened, it presents a sort of skinor cementitious film which traverses a large number of the underlyingvoids or cells in the body of the mass. This natural consequence isdecidedly detrimental and the efficiency of the product as a soundabsorber is lowered to a very marked extent.

I produce a plaster preferably according to one of the examples A, B orC, mixing the constitutents together with water until a plaster of theproper consistency is had. The plaster is then troweled into positionupon the wall to be covered and same is permitted to set and dry in theregular manner.

I now scrape over the outer or exposed surface of the wall thus formed'so as to break down, at least at many points, the aforementionedcementitious skin coat which resulted from the seepage moisture inducedby the troweling pressure. Or better still,

I employ a wire brush whose bristles are stiff and of suitabletransverse diameter, and by advancing the free ends of the bristlesagainst said skin coat While retaining suitable pressure thereagainst, Icause these bristles to penetrate the said film coat and to pass intothe body of the plaster so as to tear down all film surfaces that residein their path. In this manner, I not only reopen the exposed surface ofthe plaster, but, and as will be seen, I tear away certain of thematerial within the body of the mass or through the thickness thereof.If, incident to the trowelin process, certain of the voids are obstructeand, hence, the quality of the plaster impaired, it manifestly followsfrom the foregoing description that I re-establish lanes ofcommunication between the voids so as to bring the material to a pointof maximum efficiency as a sound absorbing plaster.

When resort is made to a scraping action as a means to open up thesurface pores, a flat steel blade can be employed whose edge portion canbe impelled manually over the exposed surface of the wall while theblade is advanced against the wall by pressure of the arm of theplasterer. WVhen use is made of a stiff bristled brush, the bristles canbe of the same transverse diameters, or they may be respectively ofdifferent diameters, some very small and others appreciably larger. Ineither instance, I rectify the mistakes which were made to presentthemsleves, as a natural consequence, when applying the plaster, and thefinished product not only is possessed of its erroneously calculateddegree of absorption, whatever that may be, but in addition thereto Ihave multiplied by many times the number of surface voids, and

aside therefrom have opened up the paths of communication within thebody of the product.

A wall constructed according to Examples Nos. 1, 2 and 3, or A, B and C,may be set up and tested when hard and dry, or at least, or preferably,while semi-dry, and if found too low in its sound absorbing property theobjection can be remedied and other tests made until the desired resultsare had. I am able to use a high bonding plaster and a low percentage ofgranular particles. The plaster can be applied like hard plaster, ornon-sound absorbing plaster. The colloidal matter, (soap),adds to thenumber of air set, so as to produce the greatest multiplicity of surfaceinterstices or voids. However, I wish to make clear that in so far asmay concern the broad phases of my invention there are other and verydesirable ways of accomplishing not only the results hereinbeforementioned but resultsthat may be had with great accuracy inconsideration of a previously calculated acoustical formula which I haveused as a pattern in the production of a wall or surface whose soundabsorbing qualities may be controlled according to a predeterminedformula or pattern. With this end in view, perforations of respectivelygraduated sizes may-be formed within the wall surface as may benecessary to meet a given condition. By graduated sizes I, of course,have reference to both the diameters of the holes to be formed, as wellas to-the depth of such holes.

On reference to Figure 1, it will be observed that the exposed face ofthe wall surface A 'is formed with a multiplicity of holes B whichextend into the thickness ofmaterial. The thin shells or films E around.

the principal voids C are likewise penetrated and broken through so thatcommunication is established between these voids and the outer face ofthe material by way of the holes B.

I claim as my invention:

1. The process of producing a sound 'absorbing wall which consists inproviding a plaster including porous granular particles that willprevent close packing and produce voids between the particles, applyingthe plaster to the surface to be covered, permitting the plaster to set,and in penetrating the exposed face of the plaster and continu-- ingthis step of penetrating the material 'to break down the hardenedsurface film induced by seepage of cementitious moisture in the act ofapplying the plaster and to break down the inner texture of the materialat the boundaries of the voids between the granular particles, wherebyto establish inter-communication between the voids and lularsound-absorbing material formed of granular particles and a gypsum base,the i said material having I openings extending from its exposed surfaceand extending into the material through the thickness thereof andtraversing the walls of adjacent cells of the material.

LYAL B. RYMARCZICK.

